1. Field of the Invention
The present invention relates to the microbial fermentation industry. More specifically, the present invention relates to a technique for imparting an ability to utilize methanol to a microorganism not inherently having such an ability or enhancing such an ability of a microorganism having such an ability at a low level, and a method for producing a target substance by utilizing methanol with use of a microorganism obtained by such a technique as mentioned above.
Substances produced according to the present invention include L-amino acids, nucleic acids, antibiotics, vitamins, growth factors, physiologically active substances and so forth, which have conventionally been produced utilizing microorganisms.
2. Brief Description of the Related Art
To date, most fermentation raw materials utilized in production of useful substances by microbial fermentation are sugars derived from agricultural products. However, since the price of sugars derived from agricultural products have been reported to be on an upward trend, an inexpensive material of good quality is desirable as an alternative fermentation raw material.
Methanol is easily dissolved in water and inexpensive, and it can be obtained at a high purity level. Moreover, it can be comparatively easily produced from methane, which is a main component of natural gas. Therefore it is preferable as a raw material for substance production. If methanol is used as a raw material for microbial fermentation, not only the cost of the principal raw material can be reduced, but also purification of products from fermentation solutions and waste solution disposal processes can be simplified. Thus, the total production cost can be reduced. Methods for producing substances, particularly amino acids, using methanol as a raw material utilizing microorganisms are known, and include a method of utilizing a microorganism of the genus Achromobacter or Pseudomonas (Japanese Patent Publication (Kokoku) No. 45-25273), a method of utilizing a microorganism of the genus Protaminobacter or Methanomonas (Japanese Patent Laid-open Publication (Kokai) No. 50-25790), a method of utilizing a microorganism of the genus Methylobacillus (Japanese Patent Laid-open Publication No. 4-91793), a method of utilizing a methylotrophic bacterium belonging to the genus Bacillus (Japanese Patent Laid-open Publication No. 3-505284, U.S. Pat. No. 6,083,728) and so forth. However, known bacterial strains have not acquired high productivity of amino acids necessary for bacteria for practical use.
Meanwhile, methods of utilizing microorganisms of the genus Brevibacterium, Corynebacterium, Bacillus or Escherichia have constituted the mainstream of amino acid production from glucose (see “Amino Acid Fermentation”, Ed. By H. Aida et al., the Japan Scientific Societies Press [Gakkai Shuppan Center], 1 st Edition, published on May 30, 1986)). These amino acid-producing bacteria are precious bacterial strains bred by introducing various mutations so that the maximum amino acid productivity is obtained while further breeding is refined for practical use. However, this can be a long time. Furthermore, these industrially-used strains cannot utilize methanol.